refactor: oop log parser

interfaces/log-parser/oop/group.go

@@ -0,0 +1,49 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"sort"
+)
+
+type group struct {
+	sum  map[string]result // metrics per group key
+	keys []string          // unique group keys
+	key  groupFunc
+}
+
+func groupBy(key groupFunc) *group {
+	return &group{
+		sum: make(map[string]result),
+		key: key,
+	}
+}
+
+// digest the results
+func (g *group) digest(results iterator) error {
+	return results.each(func(r result) {
+		k := g.key(r)
+
+		if _, ok := g.sum[k]; !ok {
+			g.keys = append(g.keys, k)
+		}
+
+		g.sum[k] = r.add(g.sum[k])
+	})
+}
+
+// each yields the grouped results
+func (g *group) each(yield resultFn) error {
+	sort.Strings(g.keys)
+
+	for _, k := range g.keys {
+		yield(g.sum[k])
+	}
+
+	return nil
+}